Populus fremontii subsp. fremontii
Plants to 30 m. Branchlets, leaf blades, and petioles glabrous or glabrate to densely hairy, hairs whitish. Neoformed leaves: blade broadly triangular-ovate, usually about as wide as long, rarely wider, base truncate or cordate, apex short-acuminate. Capsules (6–)7.5–11 mm.
Phenology: Flowering Feb–May; fruiting Mar–Jun.
Habitat: Floodplains, canyons, springs, other moist places
Elevation: (-60-)0-1500 (-2200) m
Ariz., Calif., Idaho, Nev., N.Mex., Utah, Mexico (Baja California, Baja California Sur, Sonora).
Subspecies fremontii is the common cottonwood of southwestern North America west of the Continental Divide. It intergrades with subsp. mesetae along a line from southeastern Arizona south along the border between Chihuahua and Sonora.